Time-delay magnetic trip unit for circuit breaker



Nov. 12, 1968 c. L.JENCKS ET AL 3,411,117

TIME-DELAY MAGNETIC TRIP UNIT FOR CIRCUIT BREAKER Filed Dec. 9, 1966 7A 32 I 7 5'- 0 278* o 22 W CI, 5 /45 IM 5? L I mvaurms 5 CHARLES l. l/ENC/(S, 14 l G O/765M Mesa-1. V 45 j BY C 58 FIG. 5 WM 7 A T TOR/V5 Y United States Patent 3,411,117 TIME-DELAY MAGNETIC TRIP UNIT FOR CIRCUIT BREAKER Charles L. Jencks, Avon, and George W. Kiesel, Unionville, Conn., assignors to General Electric Company, a corporation of New York Filed Dec. 9, 1966, Ser. No. 600,631 5 Claims. (Cl. 335-61) ABSTRACT OF THE DISCLOSURE An electric circuit breaker having at least one magnetic tripping means. The response time of the magnetic tripping means is determined by a dashpot which includes a rod-operated piston moving within an oil filled rigid cylinder, the oil flowing around the piston. The change in volume caused by the entrance of the rod into the cylinder as the piston moves therein is accommodated by a flexible and elastic sleeve attached to the piston rod and the cylinder wall, in effect closing the top wall of the cylinder. Fluid flows through the space around the periphery of the piston and into the elastic sleeve as the piston moves into the cylinder. On reverse movement, a one-way valve permits flow through a hole in the piston for fastresetting.

BACKGROUND OF THE INVENTION (1) Field of the invenlion Our invention relates to circuit breakers of substantial current carrying capacity and more particularly to an improved component for such circuit breakers comprising a time-delay magnetic trip unit.

Prior art circuit breakers of the type referred to have ordinarily been provided with both time-delay and instantaneous operating means which act to cause the breaker to trip upon the occurrence of predetermined current conditions. In operation, the time-delay operating means is responsive to low overload current conditions while the instantaneous operating means is utilized for the purpose of providing substantial instantaneous trip action at higher abnormal currents, such as during short-circuit conditions. In many such circuit breakers, especially of the high-current capacity type, such, for example as 2000 or more amperes normal current carrying capacity, it is desirable that a time-delay device be provided of the type including an electromagnetic actuator combined with a dashpot device to provide the time-delay.

(2) Description 0 the prior art Prior art electromagnetic time-delay operating means have been relatively expensive, largely because of the nature of the dashpot assembly utilized. Thus, for example, such dashpot assemblies have ordinarily included a bellows as a storage place or reservoir for the fluid utilized. Such bellows, which must be molded or otherwise formed of fluid-tight resilient material, are relatively expensive. In addition, in prior art circuit breakers the electromagnetic actuating means for the instantaneous acting device and for the time-delay device have required separate energizing windings.

OBJECTS OF THE INVENTION It is an object of the present invention to provide a time-delay-trip device which device includes a dashpot assembly which is simple, reliable, and relatively inexpensive to manufacture.

Another object of the invention is to provide a timedelay 'trip device which is compatible for use with instantaneous operating means present in a variety of dif- Patented Nov. 12, 1968 ferent circuit breakers without the necessity for extensive modifications therein.

A further object of the invention is to provide a circuit breaker of substantial current-carrying capacity including a time-delay operating means and instantaneous operating means, both of which are energized by the same winding.

SUMMARY OF THE INVENTION In accordance with the invention in one form, a timedelay type magnetic trip device is provided in a circuit breaker casing, on which is supported a magnetic field piece. An armature is pivotally mounted on the support in juxtaposed relation to the field piece whereby when the field piece is energized, the armature is drawn thereto. The armature is provided with an extension which engages and releases the latched operating mechanism of the circuit breaker to thereby cause tripping of the breaker. A dashpot means is fixed to the support adjacent the magnetic field piece. The dashpot means includes a movable member, one end of which is fixed to a member carried by the armature and thus movable therewith. The dashpot means is also provided with a restraining means which restrains the movement of the movable member when the latter moves in tripping direction. This restraining means comprises a dashpot including a plunger moving within a generally cylindrical chamber. The chamber is filled with a suitable fluid such as silicone oil, which is forced to flow around the piston in the relatively small clearance space between the piston and the wall. The operating rod of the piston is sealed at its entrance point into the chamber by means of a flexible tube or sleeve of enlarged diameter which is fastened in liquid-tight relation to the cylinder at one end and to the operating rod at the other. By providing a tube or sleeve of enlarged diameter, the end of the sleeve is caused to fold inwardly or involute as the rod enters the cylinder, thus providing the required sealed flexible action which would otherwise require a bellows.

In accordance with another aspect of the invention, the sleeve is made of resilient material so that it is able to expand as required to accommodate the excess fluid displaced from the cylinder by the entrance of an additional portion of the operating rod.

In accordance with another important aspect of the invention, the actuating means for the instantaneous and time-delay devices comprise magnetic field members positioned closely together and encircled by a common winding, thus simplifying the assembly.

The invention Will be more fully understood from the following detailed description, and its scope will be pointed out in the appended claims.

BRIEF DESCRIPTIONOF THE DRAWINGS In the drawings,

FIGURE 1 is a side elevation view of an electrical circuit breaker incorporating the invention, a portion of the side casing being broken away;

FIGURE 2 is a perspective view of the trip device portion of the circuit breaker of FIGURE 1;

FIGURE 3 is a sectional view of the time-delay magnetic trip unit of the present invention illustrating the dashpot portion of the trip device in the normal or unactuated condition;

FIGURE 4 is a sectional view similar to FIGURE 3 at the end of a tripping action;

FIGURE 5 is a sectional view similar to FIGURE 3 at a point approximately halfway on the return from the actuated condition of FIGURE 4 to the unactuated or normal position illustrated in FIGURE 3; and

FIGURE 6 is an exploded perspective view of a portion of the dashpot piston of the time-delay magnetic trip device of the present invention.

3 DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIGURE 1, the invention is shown as incorporated in an electric circuit breaker of the type including an insulating base portion 11 and an insulating cover 12 providing a plurality of pole chambers or lengthwise compartments 10A therein (only one shown). A multi-pole breaker is shown for convenience, but it will be understood that the invention is equally usable with single, two or three or more pole breakers.

Each of the pole chambers 10A includes a pair of relatively movable contacts, not shown, the movable contacts of all poles being ganged together for movement in unison between open and closed circuit positions. Operating mechanism, is also provided including a releasable member 13, as seen in FIGURES 1 and 2, which when released causes actuation of the remaining portions of the mechanism, not shown, and automatic opening of all of the contacts. The operating mechanism is also manually operable by means of a handle member 14.

The releasable member 13 is normally restrained in latched position by means of its engagement with a shoulder 15 on a latch member, generally designated by the numeral 16, which is pivotally mounted within the base portion 11 of the housing in a manner well known in the art. The latch member 16 is continuously biased in a clockwise direction by a spring 17 which is positioned between the latch member 16 and a portion 18 of the base 11 of the circuit breaker 10.

The common trip bar 19, which extends across all poles of the circuit breaker, carries a projection 20 which normally holds the latch member 16 against the bias of spring 17 as shown in FIGURE 1. The trip bar 19 is pivotally supported on a pivot pin 21 by means of an arm 22. Additional similar arms 22, not shown, mounted on similar pivot pins may be provided for the other poles in order to provide additional support for the trip bar 19. Rotation of the common trip bar 19 in a clockwise direction rotates the latch member 16 against the bias of spring 17 thereby freeing the releasable member 13 from its engagement with the shoulder 15 on the latch member 16, initiating automatic opening of the circuit breaker as previously described. A stop 23 is employed which engages the projection 20 and limits counterclockwise movement of the common trip bar 19 and the simultaneous clockwise movement of the latch 16, by the spring 17.

For the purpose of causing rotation of the common trip bar 19 in a clockwise direction to cause tripping of the circuit breaker in response to certain predetermined current conditions, provision is made for magnetic or instantaneous-acting tripping and also for time-delayed tripping. The instantaneous-acting device and the time-delay devices are mounted in side-by-side relation on a common support plate 24 fixed to the base portion 11 of the circuit breaker 10 by means of suitable fasteners such as screws 25 and 25A.

The instantaneous acting magnetic tripping means, generally designated by the reference number 26, comprises a generally U-shaped magnetic field piece 28 including a plurality of U-shaped laminations 29 held between two side plates comprising a generally U-shaped member 27 and a corresponding U-shaped member 30 of insulating material, by suitable means such as rivets 31. The side plate 27 is fastened to the support plate by suitable means such as by screws 25A. An armature assembly 32 is pivotally mounted on the end portion of leg 27A of U- shaped member 27 by means of pivot pin 21. The armature assembly 32 consists of an arm 33 and a plurality of armature laminations 34 held together by suitable means, such as rivets 35. The arm 33 is provided with an adjusting screw 36 at its outer end, whereby the amount of travel of the member 33 before it engages the common trip bar 19 may be adjusted. The armature assembly 32 is biased out of engagement with the field piece 4, 28 by spring 27 which has one end fixed in opening 38 suitably provided in member 33 and the other end fixed in opening 39 provided in a U-shaped member 40 secured to leg 27A by means of rivet 65.

In operation, the magnetic field piece 28 is energized by means of the current passing through a winding 41, the latter having one end connected to the line end of the circuit breaker and the other to the load end thereof in a manner well known in the art. Upon the existence of predetermined current conditions, such as high overload current, the pull of. the magnetic field piece 28 on the armature 32 becomes sufficiently strong to override the bias of spring 37 and thereby cause the armature assembly 32 to pivot clockwise about pivot pin 21. When this occurs, the member 33 engages the common trip bar 19 moving the bar 19 clockwise thereby causing the unlatching of the releasable member 13 in the manner previously set forth resulting in substantially instantaneous tripping of the circuit breaker.

The time-delay magnetic trip device, generally designated by reference numeral 42, is also mounted on the support plate 24 in side-by-side relation to the instantaneous magnetic tripping means 26. The basic elements of the trip device 42 include a magnetic field piece 43, an armature assembly 44, and a dashpot assembly 45. The field piece 43 which is essentially similar to the magnetic field piece 28 of the magnetic tripping means 26, comprises a substantially U-shaped side support plate member 46 and a plurality of U-shaped laminations 47 held together in intimate contact with the U-shaped plate of insulation 30 by suitable fastening means, not shown. The U-shaped member 46 also has one leg 46A which is longer than the other in order to provide a support for pivot pin 21 on which is pivotally mounted the armature assembly 44. The other end portion of the U-shaped member 40 is also secured to the extended portion of the leg 46A by means of a rivet 48.

The armature assembly 44 comprises an arm 49 and a plurality of armature laminations 50. The armature assembly 44 is biased away from the field piece 43 by means of a spring 51 which has one end fixed to the arm 49 and the other to the U-shaped member 40 in a manner similar to that previously described with reference to spring 37 of the magnetic tripping means 26. The arm 49 also is provided with an adjusting screw 52 whereby the amount of travel of the armature assembly 44 before it engages the common trip bar 19 may be adjusted. It will be observed that up to this point the structure and operation of the time-delay magnetic trip device 42 is essentially identical to that of the instantaneous magnetic trip device 26. That is, the magnetic field piece 43- when energized by current passing through the 'winding 41, the latter being common to both the field piece 28 and the field piece 43, will exert a pull on the armature assembly 44 whereby when predetermined current conditions exist, the pull of field piece 43 will be sufiiciently strong to override the bias of spring 51 thereby pivoting the armature 44 clockwise about pivot pin 21 resulting in tripping of the circuit breaker in the manner previously set forth with reference to instantaneous magnetic tripping means 26.

The function of the dashpot assembly 45 is to resist the clockwise movement of the armature 44 and thereby provide a time delay in the tripping action of the unit 42. The function performed by this time delay is similar to that performed by a thermal operating means in conventional thermal type circuit breakers in that it occurs upon the existence of predetermined current and time conditions, namely low overload current conditions which are sustained for predetermined times.

Referring now to FIGURES 3-6, the dashpot assembly 45 includes a shaft 53, one end of which is fixed to member 49 of the armature 44 by a pivot pin 54 whereby the pivotal movement of the armature 44 is translated into an up-and-down movement of the shaft 53. The other end of the shaft 53 has secured thereto a piston 55 comprising a rubber washer valve 56, the functions of which will be more fully described hereinbelow.

The dashpot assembly 45 further comprises a housing 57 which is secured to support plate 24 by screws 58, and a rubber shaft seal and expandable reservoir 59 by spring clips 60 and 61, respectively. The housing 57 and the expandable reservoir 59 are substantially completely filled with a suitable liquid, such, for example as silicone oil. A gasket 62 is interposed between the housing '57 and the support plate 24 to provide a liquid-tight seal at this poillt.It should be noted particularly with reference to FIGURES 3-5 that a substantial clearance exists between the shaft 53 and the housing 57, and similarly between the piston 55 and the housing 57. Also, as can be seen with reference to FIGURE 6, the piston 55 is provided with a plurality of holes 64 which extend through the piston 55 from one side thereof to the other.

The operation of the dashpot assembly 45 will now be described with reference to FIGURES 35. FIGURE 3 shows the position of the components of the dashpot assembly 45 at the start of the tripping action, i.e., in its normal, unactuated, condition. The shaft 53 is moved downwardly by clockwise movement of the armature 44 resulting from the pull exerted by the field piece 43. As the 'shaft 53 moves downward, the oil 63 is forced past the piston 55 through the clearance between the piston 55 and the housing 57. The time-delay characteristic of the magnetic trip unit 42. is a function of this clearance between the piston 55 and the housing 57. Thus, if a large clearance exists, the shaft 53 will move downwardly more rapidly than if the clearance is small because of the greater amount of freedom with which the oil 63 will be able to: move upwardly. Inasmuch as the dashpot assembly 45 exerts a direct restraining force on the clockwise movement of the armature 44, adjustment of the amount of clearance between the piston 55 and the housing 57 will have the same effect on the movement of the armature 44 as it does on the shaft 53.

FIGURE 4 shows the position of the components of the dashpot assembly at the end of the clockwise movement ,of the armature 44, and after tripping of the circuit breaker. It will be observed that the rubber shaft seal 59 has rolled over or collapsed inwardly at the top, thus permitting the longitudinal movement of the shaft 53. The rubber shaft seal or reservoir 59 has also expanded due to the additional oil 63 that has beenforced upwardly out of the housing 57 because of the additional volume of the shaft 53 being forced down into the housing '57. It should also be noted that in the position illustrated in FIGURE 4 clearance exists between the end of shaft 53 and the gasket 62.

The shaft 53 along with the other components of the dashpot assembly 45 are returned to the normal position, that is, the position shown in FIGURE 3, by means of the spring 51 of the armature 44 whenthe pull ofthe field piece 43 is' no longer strong enough to override the bias of spring 51. FIGURE 5 shows the components of the dashpot assembly 45 at a point halfway along this return stroke. The'oil 63 is now being forced from above the piston to the bottom of the housing '57. This forces the rubber valve washer 56 to open and thus creates an additional oil flow area through the holes 64 in the piston 55. This provides for a much faster return stroke.

Although only one magnetic tripping means 26 and one time-delay magnetic trip unit 42 have been illustrated, it will be understood that the invention contemplates providing each pole of a multipole breaker with such magnetic tripping means and time-delay magnetic trip unit.

Thus, in accordance with the invention, there is provided a time-delay magnetic trip for use with circuit breakers of substantial current carrying capacity which in association with magnetic operating means provides a circuit breaker with either delay time reaction or instantaneous trip action depending on the occurrence of predetermined circuit conditions.

While the invention has been shown in only one particular embodiment, it will be apparent that many modifications thereof may be made, and we therefore intend by the appended claims to cover all such modifications as fall within the true spirit and scope of the invention.

What we claim as new and desire to secure by Letters Patent of the United States is:

1. An electric circuit breaker comprising:

(a) means releasable to cause automatic opening of said circuit breaker;

(b) latching means connected to said releasable means,

said latching means normally restraining said releasable means;

(c) at least one magnetic tripping means connected to said latching means, said magnetic tripping means rotating said latching means upon the occurrence of predetermined current conditions to thereby free said releasable means to cause automatic opening of said circuit breaker;

((1) said magnetic tripping means comprising a magnetic field piece, an armature pivotally supported for movement toward said field piece upon the occurence of said predetermined current conditions, and dashpot means connected to said armature;

(e) said armature having a portion connected to operate said latching means as said armature moves toward said field piece;

(f) said dashpot means resisting said movement of said lanrnature toward said field piece to thereby provide said magnetic tripping means with a time-delay characteristic and said dashpot means having means operable when said armature moves in a direction away from said field piece to permit uninhibited movement of said armature in said direction;

(g) said dashpot means comprising a housing having a hollow interior, a shaft member having one end fixed to said armature for movement therewith, an expandable member having one end fixed to said shaft member and the other end fixed to said housing, and fluid means;

(h) said shaft member having a piston supported on the other end thereof;

(i) said expandable member having .a substantially greater volume than said shaft member;

(j) said fluid means occupying the interior of said housing and the interior of said expandable member other than that occupied by said shaft member; and

(k) said expandable member being expanded by said fluid means as said armature moves toward said field piece.

2. An electric circuit breaker as defined in claim 1 wherein:

(a) said piston has a plurality of openings extending therethrough;

(b) one-way valve means are supported on said shaft member in juxtaposed relation to said openings in said piston, said valve means preventing the passage of said fluid means through said openings as said armature moves toward said field piece and permitting the passage of said fluid means through said openings as said armature moves away from said field piece; and

(c) said expandable member comprising an involuting sleeve, said involuting of said sleeve occurring as said armature moves toward said field piece.

3. An electric circuit breaker comprising:

(a) means releasable to cause automatic opening of said circuit breaker;

(b) rotatable latching means connected to said releasable means, said latching means normally restraining said releasable means;

(c) a first magnetic tripping means and a second magnetic tripping means each connected to said latching means;

((1) said latching means being rotated by either of said magnetic tripping means upon the occurrence of predetermined current conditions to thereby free said releasable means to cause automatic opening of said circuit breaker;

(e) a winding having one end connected to the line end of said circuit breaker and the other end connected to the load end of said circuit breaker;

(f) said first magnetic tripping means comprising a magnetic field piece, an armature pivotally supported for movement toward said field piece upon the occurrence of low overload current conditions and dashpot means connected to said armature resisting said movement of said anm ature toward said field piece to thereby provide said first magnetic tripping means with a time delay characteristic;

(g) said second magnetic tripping means comprising a magnetic field piece and an armature pivotally supported for movement toward said field piece upon the occurrence of high overload current conditions to cause substantially instantaneous opening of said circuit breaker;

(h) said winding encircling at least a portion of said magnetic field piece of both of said first and second magnetic tripping means;

(i) said dashpot means comprising a housing having a hollow interior, a shaft member having one end fixed to said armature for movement therewith, an expandable member having one end fixed to said shaft member and the other end fixed to said housing, and fluid means;

(j) said shaft member having a piston supported on the other end thereof;

(k) said expandable member having a substantially greater volume than said shaft member;

(1) said fluid means occupying the interior of said housing and the interior of said expandable member a other than that occupied by said shaft member; and

(In) said expandable member being expanded by said fluid means as said armature moves toward said field piece.

4. A multipole circuit breaker comprising:

(a) means releasable to cause automatic opening of said circuit breaker;

(b) latching means connected to said releasable means,

said latching means normally restraining said releasable means;

(c) a plurality of magnetic tripping means connected to said latching means, said latching means being rotated by any one of said plurality of magnetic tripping means upon the occurrence of predetermined current conditions in any one pole of said multipole circuit breaker to thereby free said releasable means to cause automatic opening of said circuit breaker;

(-d) each of said magnetic tripping means comprising a magnetic field piece, an armature pivotally supported for movement towardsaid field piece upon the occurrence of said predetermined current conditions, and dashpot means connected to said armature;

(e) said armature having a portion connected to operate said latching means as said armature moves toward said field piece;

(f) said dashpot means resisting said movement of said armature toward said field piece to thereby provide said magnetic tripping means with a time delay characteristic, and said dashpot means having means operable when said armature moves in a direction away from said field piece to permit uninhibited movement of said armature in said direction; 1

(g) said dashpot means comprising a housing having hollow interior, a shaft member having one end fixed to said armature for movement therewith, an expandable member having one end fixed to said shaft member and the other end fixed to said housing, and fluid means;

(h) said shaft member having a piston supported on the other end thereof;

(i) said expandable member having a substantially greater volume than said shaft member;

(j) said fluid means occupying the interior of said housing and the interior of said expandable member other than that occupied by said shaft member; and

(k) said expandable member being expanded by said fluid means as said armature moves toward said field piece.

5. A multipole circuit breaker as defined in claim 4 wherein:

ting the passage of said fluid means through said openings as said armature moves away from said field piece; and

' (c) said expandable member comprising an involuting sleeve, said involuting of said sleeve occurring as said armature moves toward said field piece.

References Cited UNITED STATES PATENTS 1,344,199 6/1920 Cheney 335-61 1,942,040 1/ 1934 Wolff 20083 2,632,823 3/1953 Oppel 335-62 BERNARD A. GILHEANY, Primary Examiner.

HAROLD BROOME, Assistant Examiner. 

